Electronic devices such as an organic electroluminescent element (so-called an organic EL element) utilizing electroluminescence of an organic material (hereinafter, described as EL) and an organic photoelectric conversion element have a configuration in which an organic material layer or a photoelectric conversion layer is sandwiched between two electrodes. In the organic EL element, emitted light generated in the organic material layer (a light-emitting layer) passes through the electrode and is taken out to the outside. In addition, in the organic photoelectric conversion element, light from the outside passes through the electrode and is taken into the photoelectric conversion layer. Therefore, in these electronic devices, it is necessary that at least one out of two electrodes is constituted of a translucent electrode.
On the other hand, as a form of thin-type/light-weight organic EL element, a solid sealing is known (for example, refer to Patent Literature 1 and Patent Literature 2). In the solid sealing, there are pressurization/heating processes, and thus an unevenness of the electrode has a large influence on leak characteristics. Therefore, a particularly smooth translucent electrode becomes necessary.
In response to such a request, a technology of using an ITO electrode on a flexible base material and further obtaining a smooth surface of an electrode by using a polishing tape is disclosed (for example, refer to Patent Literature 3). However, in the method, a smoothening process by the polishing tape becomes troublesome, and the productivity becomes a problem. Additionally, the ITO on the flexible base material exhibits insufficient properties as an electrode because of a restriction on conditions of film formation.
As a means of improving properties of an electrode, a technology of using a thin Ag layer as an electrode is disclosed (for example, refer to Patent Literature 4). Although the Ag layer is formed at a temperature lower than that of ITO and excellent in anode properties, since the thickness is as small as 30 nm or less and Ag is a flexible metal, and thus the Ag layer is apt to be affected by pressurization/heating at the time of solid sealing, and there exists a problem of maintaining smoothness of the electrode.
A technology of smoothening a barrier surface on a flexible base material as a smooth electrode base layer (for example, refer to Patent Literature 5) is known in order to solve such a problem. In Patent Literature 5, a technology of smoothening a surface depending on CVD conditions in forming an evaporation barrier film is disclosed. However, a layer formed by the CVD method as the method has an insufficient smoothness due to the principle of a CVD method, and greatly receives an influence of pressurization/heating at the time of solid sealing to thereby deteriorate leak characteristics. As described above, in a vapor evaporation method such as a CVD method, film formation is carried out by deposits, and thus it is difficult to obtain conditions that satisfy the smoothness of a thin Ag electrode, capable of withstanding a solid sealing process.
On the other hand, a technology of smoothing the barrier surface by an inorganic-organic hybrid polymer is disclosed (for example, refer to Patent Literature 6). According to the method, although the smoothening by a film becomes reliably possible, the polymer of a smooth protecting layer deforms locally due to heating/pressurizing in the solid sealing and the smoothness of the electrode cannot be maintained.